1. Field of the Invention
The present invention relates to a device for aligning a stack of flat workpieces, and more particularly to a mechanism for moving two alignment devices simultaneously in opposite directions. Such alignment devices have vertical parallel faces for stacking identical flat workpieces having two opposite parallel faces, and are operated by an oscillating drive mechanism through two respective parallel slides secured to the drive mechanism by respective toggle mechanisms.
One application of the invention is in the package-making industry. Cardboard packages for products such as cigarettes are printed on their surfaces, then creased along intended folding lines and, finally, accurately die-cut to the required external shape. In this state, they are delivered to the cigarette manufacturer where they will be shaped during the processing operation of the cigarettes. However, after performance of the above-mentioned operations i.e., the printing, creasing, and die-cutting, the flat blanks have to be stacked at the end of the production line.
2. Related Art
Conventional equipment for this application employs alignment devices having vertical parallel faces arranged on opposite sides of the stack of flat workpieces, for simultaneously applying two opposed pressures on the accumulating stack in order to align the opposed edges of the flat workpieces.
It is very difficult to control the alternating movements of the two alignment devices in perfect phase opposition, i.e., so that the aligning forces are applied and withdrawn simultaneously. It is important to do so, however, because a slight phase difference imparts an oscillating movement to the stack which, finally, threatens to fall.
To avoid this problem, it has been proposed to connect the alignment devices with an oscillating driver by two respective parallel slides, articulated with regard to the driver around two respective toggle axles which are symmetrical and parallel to the oscillating axle of the driver. Such a solution ensures, initially, the required synchronism between the jointed axles and the jointed pieces on these axles until a clearance appears by wear. As this clearance increases, the phase difference between the operation of alignment devices increases, and hence, the problem reappears.
The aim of the present invention is to meet, at least partly, the aforementioned drawbacks.
According to the invention, there is provided a mechanism for moving two alignment devices having vertical parallel faces for stacking identical flat workpieces, simultaneously in opposite directions. The mechanism includes two reciprocating slides that simultaneously drive the alignment devices in opposite directions. The slides are operated by an articulated mechanism including a pair of extension arms and a drive cradle attached to an oscillating shaft. Arcuate projections on the drive cradle engage rotationally with complementary arcuate surfaces on coupling mechanisms attached to the extension arms as the shaft oscillates. Compression springs bias the extension arms and the associated coupling mechanisms against the projections to eliminate the effect of wear in the mechanism.